Touch panel technology is rapidly being adopted today in cell-phone displays and other screens for electronic devices. However, a problem with touch panels is that the screen is in an exposed state, creating numerous opportunities for direct contact with the fingers, cheeks, etc. and readily allowing contaminants such as skin oils to adhere. To improve appearance and visibility, there has been a growing need for ways in which to make it harder for users to leave fingerprints on the surface of a display and easier to remove smudges, leading to a desire for new materials that can address such demands. In particular, because fingerprints readily form on touch panel displays, it is desired that a water/oil repellent coat be provided on the display. Unfortunately, conventional water/oil repellent coats have a high water and oil repellency and excellent contaminant wipeability, but the anti-smudging performance diminishes during use.
Fluoropolyether group-containing compounds have a very low surface free energy, and thus generally possess such attributes as water and oil repellency, chemical resistance, lubricity, parting properties and anti-smudging properties. These qualities are widely used industrially in, for example, water/oil-repellent stain-proofing agents for paper and textiles, lubricants for magnetic recording media, oil-proofing agents for precision machinery, parting agents, cosmetics and protective coats. However, these same qualities also manifest as non-tackiness and non-adherence to other substrate materials. Therefore, even when such compounds can be applied to the surface of a substrate, inducing the resulting coat to adhere to the substrate has been a challenge.
Of related interest here are silane coupling agents, which are familiar as substances that bond together substrate surfaces such as glass or fabric with organic compounds and are widely used as coatings for various types of substrate surfaces. Silane coupling agents have an organic functional group and a reactive silyl group (generally a hydrolyzable silyl group such as an alkoxysilyl group) on the same molecule. The hydrolyzable silyl group gives rise to a self-condensing reaction due in part to moisture in the air, forming a film. The hydrolyzable silyl groups in this film bond chemically and physically with the surface of the glass, metal or the like, resulting in a strong and durable coat.
JP-A 2008-534696, JP-A 2008-537557, JP-A 2012-072272, JP-A 2012-157856 and JP-A 2013-136833 disclose compositions which, by making use of a fluoropolyether-containing polymer-modified silane obtained by introducing a hydrolyzable silyl group onto a fluoropolyether group-containing compound, are able to form a coat that readily adheres to a substrate surface and imparts the surface of the substrate with water and oil repellency, chemical resistance, lubricity, parting properties and anti-smudging properties.
The cured film on a lens or anti-reflective coating that has been surface-treated with such a composition containing a fluoropolyether-containing polymer-modified silane obtained by introducing a hydrolyzable silyl group onto a fluoropolyether-containing compound has excellent lubricity and parting properties. However, cured films produced by a wet coating process such as spray coating or dip coating are unable to demonstrate sufficient abrasion resistance compared with cured films produced by vapor deposition.